EP1978112B1

EP1978112B1 - Systems and methods for providing localized heat treatment of gas turbine components

Info

Publication number: EP1978112B1
Application number: EP08250939.9A
Authority: EP
Inventors: Thomas Demichael
Original assignee: United Technologies Corp
Current assignee: Raytheon Technologies Corp
Priority date: 2007-03-30
Filing date: 2008-03-18
Publication date: 2016-12-14
Anticipated expiration: 2028-03-18
Also published as: SG146523A1; US8058591B2; US20090065494A1; EP1978112A1

Description

BACKGROUND

The manufacture, service and/or repair of gas turbine engines oftentimes requires localized heating of specified areas of engine components to allow for stress relief, metal forming and/or brazing applications. Localized heating is preferred when processing the entire component in an isothermal heat treatment oven could adversely affect the metallographic properties of the materials of the component.
In this regard, prior art localized heating methods include resistance and induction heating. Induction heating methods tend to be costly, afford little process control, and require extensive experience of an operator in order to match induction coils to both the induction generator and the component/cross sectional area being heated. In contrast, resistance heating is somewhat limited in that the power supplies are current matched to specific heating element designs. The necessity in the prior art of matching the power supplies and the heating elements has typically resulted in rather generic heating assemblies in the form of blankets that typically are much larger than the areas that require heating.
Methods of heat treatment of gas turbine components are disclosed in US-A-4611744 and EP-A-1253289 .

SUMMARY

Systems and methods for providing localized heat treatment of gas turbine components are provided. In this regard, a method in accordance with the invention is defined in claim 1.
A system in accordance with the invention is defined in claim 15.
Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. While several embodiments are described in connection with these drawings, there is no intent to limit the disclosure to the embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications and equivalents.

FIG. 1 is a schematic view of an embodiment of a resistance heating element.
[0001] FIG. 2 is a schematic diagram depicting an embodiment of a turbine case section of a gas turbine engine with the resistance heating element of FIG. 1 positioned to locally heat selected portions of the casing.
FIG. 3 is a schematic diagram of an embodiment of a system for providing localized heat treatment.
FIG. 4 is a schematic diagram of an embodiment of a cooling device.

DETAILED DESCRIPTION

As will be described in detail here with respect to several exemplary embodiments, systems and methods for providing localized heat treatment of gas turbine components are provided. In this regard, FIG. 1 depicts an exemplary embodiment of a resistance heating element 100. Element 100 is generally formed of a length of wire 102 (e.g. NiCr wire) that is attached to one or more insulators 104 (e.g., ceramic insulators). In this embodiment, multiple insulators are provided, each of which is generally cylindrical in shape and includes a hollow interior through which the wire is threaded. Depending upon the particular electrical and heating properties desired, various sizes, shapes, gauges and configurations of wire and insulators can be provided.
The embodiment of Fig 1 has been designed to provide localized heating to two areas that are spaced from each other. Notably, element 100 provides a first heating zone 110 that is spaced from a second heating zone 112, with a gap 114 being located therebetween. Note that a single row of insulators and an associated length of wire electrically interconnects the first and second heating areas, thereby providing electrical continuity to the element.
In contrast to prior art resistance heating elements, which are current-matched to their respective power sources, various configurations of resistance heating elements, such as element 100, can be used with the same power source, details of which will be discussed later.
The configuration of the embodiment of FIG. 1 may be particularly well suited for various applications, such as the exemplary application depicted in FIG. 2. As shown in FIG. 2, a section of gas turbine casing 200 includes several repair welds, such as welds 202, 204, 206 and 208, as well as welds 210, 212 and 214 that are positioned underneath heating element 100. The element 100 is attached to the turbine casing so that heat can be directed toward the welds in order to provide stress relief to the material associated with the welds. In order to facilitate attachment of the element to the casing, various techniques can be used, such as high temperature tape or stainless steel wire for example. Notably, the resistance heating element is electrically connected to a power controller (not shown) that provides current-limited electrical power to the element. Various aspects of the power controller will now be described with respect to FIG. 3.
As depicted in FIG. 3, an embodiment of a system 300 for providing localized heat treatment comprises a power controller 302, a resistance heating element 304, a thermocouple 306, and a non-oxidizing environment 308. The power controller receives a voltage input from a power source 310, which can be a conventional 110 volt outlet in some embodiments. The power controller converts the input to a current-limited output using a current limiter 312 that, in some embodiments, can be a silicon controlled rectifier (SCR). Notably, such an SCR can be controlled either by a manually controlled input, such as via a potentiometer, or by a proportional-integral-derivative (PID) controller. By altering output of the power controller 302, temperature control through heat-up, soak and cool down cycles can be provided.
It should be noted that the component that is to be heat treated is located within non-oxidizing environment 308. By way of example, such an environment can be formed by a heat resistant enclosure that is flooded with an inert gas, such Argon. For performing heat treatments, the component 314 is placed within the non-oxidizing environment and one or more heating elements are attached to the component as described before with reference to FIG. 2. Thermocouple 306 also is attached to the component, in a vicinity of the heating element, so that heating can be monitored.
Optionally, thermal insulation 316 (e.g., Fiberfrax insulation) is used to cover the heating element in order to reduce heat dissipation from the area that is to be heat-treated. Additionally or alternately, a cooling device 318 can be used to provide localized cooling, such as to areas adjacent to those areas that are to be heat-treated. In some embodiments, the cooling device can be a cooling fan and or a closed-loop cooling system, such as one that uses a liquid (e.g. water), for providing cooling.
An exemplary embodiment of a cooling device is partially depicted in FIG. 4. As shown in FIG. 4., a heat exchanger portion 400 of a cooling device is attached to a gas turbine component to provide localized cooling of the component. The cooling device includes a liquid inlet 402 that provides a flow of cooling fluid to conduit 404, which is thermally coupled to a heat exchange surface 406. Thermal energy from the heat treatment is transferred via the heat exchange surface to the cooling liquid, which is then returned to a circulating pump (not shown) after departing the conduit via a liquid outlet 408.
It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.

Claims

A method for providing localized heat treatment for a gas turbine turbine casing (200; 314) said method comprising:
identifying a plurality of welds on a gas turbine turbine casing to which localised heat treatment is to be performed, which welds include a first identified weld (202) and a second identified weld (204) separated from said first identified weld (202) by a gap;

configuring a resistance heating element (100; 304) to provide a plurality of localised heating zones including a first heating zone (110) and a second heating zone (112) separated by a gap, wherein the resistance heating element (100;304) comprises a wire (102) and a plurality of ceramic insulators (104), and wherein each heating zone (110,112) is formed by a portion of the wire (102) and some of the ceramic insulators (104);

positioning said resistance heating element (100; 304), such that the first heating zone is adjacent the first identified weld (202) and the second heating zone is adjacent the second identified weld (204);

electrically coupling a current-limiting power controller (302) to the resistance heating element (100; 304); and

locally heating the first identified weld using the first heating zone of the resistance heating element (100; 304) and the second identified weld using the second heating zone of the resistance heating element, with power being provided to the resistance heating element (100; 304) via the current -limiting power controller (302).
The method of claim 1, wherein the current-limiting power controller (302) comprises a silicon controlled rectifier.
The method of claim 1 or 2, further comprising electrically coupling the current-limiting power controller (302) to an AC power source (310) prior to performing the heating.
The method of any preceding claim, wherein:
the method further comprises positioning the gas turbine turbine casing (314) within an inert gas environment (308); and

locally heating the area is performed in the absence of oxygen.
The method of claim 4, wherein the inert gas is Argon.
The method of any preceding claim, further comprising wrapping the area and the resistance heating element (304) in thermal insulation (316) prior to the heating.
The method of any preceding claim, further comprising cooling a portion of the turbine casing (314) during the heating.
The method of claim 7, wherein the cooling is performed by a closed-loop cooling device (318) positioned adjacent the portion that is to be cooled.
The method of any preceding claim, wherein the wire (102) is NiCr wire (102).
The method of claim 9, wherein the resistance heating element (100) comprises a length (102) of NiCr wire threaded through cylindrical ceramic insulators (104).
The method of any preceding claim, wherein the heating is performed by manually adjusting output of the current-limiting power controller (302).
The method of any preceding claim wherein:
the resistance heating element comprises wire (102) and at least one ceramic insulator (104); and

the current-limiting power controller is not electrically matched to the resistance heating element (100; 304) such that various other resistance heating elements of various electrical characteristics are usable with the current-limiting power controller (302).
The method of claim 12, further comprising assembling the resistance heating element to accommodate a configuration of the area that is to be heat treated.
A system for providing localized heat treatment to first and second welds of a gas turbine turbine casing, said first and second welds separated by a gap, wherein the resistance heating element (100;304) comprises a wire (102) and a plurality of ceramic insulators (104), and wherein each heating zone (110,112) is formed by a portion of the wire (102) and some of the ceramic insulators (104) said system comprising:
a resistance heating element (100; 304) having a wire (102) and plurality of ceramic insulators (104) said resistance heating element configured to have a first localised heating zone and a second localised heating zone separated from said first localised heating zone by a gap, each localised heating zone including a portion of the wire (102) and a plurality of the ceramic insulators (104), the first and second heating zones being serially connected together across the gap by a portion of the wire (102) and a row of ceramic insulators (104); and

a current-limiting power controller (302) having a silicon controlled rectifier, the power controller (302) being operative to receive electrical power from an AC power source (310) and to provide current-limited electrical power to the resistance heating element (100; 304).
The system of claim 14, further comprising means (400) for cooling a portion of a gas turbine component located in a vicinity of an area of the gas turbine component that is to be heat treated.
The system of claim 15, wherein the means (400) for cooling is a closed-loop cooling device.
The system of claim 14, 15 or 16, further comprising a chamber (308) into which the gas turbine turbine casing is to be positioned, the chamber being operative to receive a flow of inert gas such that oxygen is purged from about the gas turbine turbine casing (200; 314) during heat treatment.